Add ShowFrom and HideFrom filters to profile filter lib.

[lvng]

• Added HideFrom and ShowFrom.
• They are not yet exposed as command line flags. This change is pretty big so I thought it would be helpful to keep it minimal but I could add that here if desired.
• Added lots of test cases for interactions between filters, as well as handling of locations with empty lines.

[aalexand]

Could you squash your initial commit history and re-push? It's just noise.

[codecov-io]

Codecov Report

Merging #360 into master will increase coverage by 0.32%.
The diff coverage is 98.09%.

@@            Coverage Diff             @@
##           master     #360      +/-   ##
==========================================
+ Coverage   66.64%   66.97%   +0.32%     
==========================================
  Files          36       36              
  Lines        7448     7528      +80     
==========================================
+ Hits         4964     5042      +78     
- Misses       2082     2083       +1     
- Partials      402      403       +1

Impacted Files	Coverage Δ
internal/driver/driver_focus.go	84.87% <100%> (ø)	⬆️
profile/filter.go	89.61% <98.07%> (+6.12%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 6167805...136ac67. Read the comment docs.

[lvng]

To squash the history I copied changes into a separate PR: #361